In automated machining of parts such as engine components, the machining takes place at machine stations, each station enclosed to form a booth. A coolant/lubricant liquid is sprayed onto the part during the machining operations in order to reduce friction and cool the part.
This spraying creates a fine mist which is intended to be confined within the booth in order to prevent the mist from being dispersed into the air within the plant, where it could be inhaled by plant personnel and present a health hazard. Also, the mist can condense onto adjacent surfaces, creating a maintenance burden.
Oil in the coolant/lubricant can also evaporate from the mist into the air and create an air pollution problem.
In order to minimize this effect, the conventional practice has been to constantly draw a large volume of air out of the booths and into ducting with a fan driven by a powerful electric motor drawing considerable power. This is intended to prevent the mist from dispersing into the air in the plant. The ducting leads to a central filter/demister where the mist is completely removed from the air before being discharged back into the atmosphere.
The coolant/lubricant condensed from the mist is collected and directed back to the machine station for reuse.
It has heretofor been recognized that it is advantageous to remove as much mist as possible at a location close to the machine tool station rather than transporting all of it to a central demisting location in order to reduce the quantity of mist transported through the ducting to the central unit. This is because leaking of condensed mist from the ducting, and evaporation of the oil in the mist into the air can both occur in the ducts, which effects will contribute to the air pollution problem mentioned above. In addition, condensed water can aid the growth of mold and creation of a fire hazard. Also, less mist flowing in the ducts reduces the maintenance efforts required in cleaning the ducting through which the mist flows.
Furthermore, high efficiency air filters (HEPA) are used to completely remove the residual mist, and these filters would rapidly become blocked if all of the mist were to reach those filters, greatly increasing maintenance costs since HEPA filters are very expensive.
A decentralized demister arrangement is described in U.S. Pat. Nos. 8,266,945 and 7,727,295, incorporated herein by reference, as well as in a TMI brochure published in 2002, referenced in those patents.
The volume of air flow drawn out of a CNC machine booth is conventionally set at a high flow rate which is thought necessary to prevent escape of oily mist from the machining booth at any time during the machine cycle, and also to insure proper operation of the cyclonic separator.
That is, the cyclonic separators typically used have usually required high air flow rates through them in order to be effective.
It is an object of the present invention to provide a demister arrangement for machine tool installations which greatly reduces the power consumption required while insuring that no mist escapes from the machining booth at any time.